John McCawley wrote:
Table orders defines the column order_code as a serial, which simple
makes a trigger which gives a new value to the column on insert. Note
that there is NO guarantee that ths column will be unique. You can
manually update the value to whatever you want. If you wish this
column to be unique, you must specify it on creation, or later do an
alter table add constraint to the column.
A foreign key requires that the referenced column be unique (DB
enforced, not just coincidentally unique), and that' s why your table
creation is failing.
[cut]
that was my misunderstanding
thanks for your reply,
Gianluca Riccardi
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